Method for operating mass comparator with removable climate module

ABSTRACT

A mass comparator including a weighing chamber ( 16 ); a draft shield ( 18, 20, 22 ), which surrounds the weighing chamber; a climate module ( 34 ), which is detachably disposed in the weighing chamber; a processor ( 32 ), a data input unit, and a data transmission path, over which data is exchanged between the climate module and the processor. The processor is programmed to use the air pressure, the air humidity and the air temperature in the weighing chamber to determine, based on the density of a substance to be weighed, an air buoyancy of at least one test sample and/or a buoyancy correction factor. Also disclosed are a climate module configured to electrically yet detachably couple to a mass comparator, and a method for operating a mass comparator including determining the air buoyancy and/or the buoyancy correction factor.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 15/149,922, which was filed on May 9, 2016, and which is a Continuation of International Application PCT/EP2014/002855, which has an international filing date of Oct. 22, 2014. The disclosures of both applications are incorporated in their entireties into the present divisional by reference. The following disclosure is also based on and claims the benefit of and priority under 35 U.S.C. § 119(a) to German Patent Application Nos. DE 10 2013 018 767.2, filed Nov. 8, 2013, and to DE 10 2014 101 565.7, filed Feb. 7, 2014, which are also incorporated in their respective entireties into the present divisional by reference.

FIELD OF THE INVENTION

The invention relates to a mass comparator and a method for operating a mass comparator comprising a weighing chamber, which is separated from the surrounding area by a draft shield. In addition, the invention relates to a climate module of such a mass comparator.

BACKGROUND

Electronic mass comparators, which relate to the present invention, work with a comparison measurement. A known mass is compared, as a reference object, with the mass of a test sample in several weighing steps. Such test samples are, in particular, the reference masses for other balances. The present invention relates, in particular, to high resolution electronic mass comparators for mass comparisons, for example, for the accuracy classes E1 to F2 in compliance with OIML R 111-1 [OIML=International Organization on Legal Metrology]. For these mass comparisons the air density, which affects the buoyancy of the weights, i.e. the sample to be weighed, is determined using external climate sensors.

With respect to mass comparators it is known that the air buoyancy is determined by a comparison measurement of two reference objects having a mass and density that are already known beforehand.

It is also known that the temperature, the air pressure and the humidity also affect the balance itself, in particular, the load cell. For this reason, in order to compensate for the variations in the balance display with changing ambient parameters, correction factors are stored in the device, for example, in the form of curves or tables. In addition, temperature and air humidity sensors are disposed, in particular, in the area of the load cell. Then these temperature and air humidity sensors are used to automatically correct the balance itself, as a function of the changing ambient conditions, also called climate changes.

Thus, for example, the German patent DE 37 14 540 C2 describes a method for automatically calibrating a high resolution electronic balance, wherein such environmental factors as the temperature change and the humidity change, both of which are detected from the outside, are used in order to calibrate the balance itself. The corresponding calibration factor is determined by a computer and corrects the weighing result.

The German patent DE 299 12 867 U1 discloses an analytical balance with a measuring sensor for ambient parameters. In this case the analytical balance has a display that is provided on the rear wall of the weighing chamber. The display shows the temperature in the weighing chamber and the air humidity in the weighing chamber as well as in general the air pressure that is usually present. In this case it is assumed that, when the air is wet, the surface of the sample to be weighed will be covered with moisture, which is a function of the variances in the air humidity. Therefore, the operator is informed by the display that, for example, with changing air humidity, the sample to be weighed should remain in the weighing chamber longer, in order to obtain a stable end value of the surface moisture. If there are extreme fluctuations in the air pressure, then the operator can perform a so-called buoyancy correction by feeding the displayed data to a processor in the balance by via of an input unit. With respect to the temperature, this temperature is used to determine the deviation from the reference temperature and to consider corresponding correction factors.

Finally, there are also climatized measuring chambers, in which there are precision balances, into which the climate data of the measuring chamber are entered. The climate data from the climate module or the sensors thereof are fed manually or automatically into the balance.

SUMMARY

An object of the present invention is to provide a mass comparator that is compact and that ensures an improved measuring accuracy with less complexity.

This object, according to one formulation of the invention, is achieved with a mass comparator, comprising a weighing chamber; a draft shield, which surrounds the weighing chamber; a climate module, which includes an air pressure sensor, an air humidity sensor and an air temperature sensor and which is disposed in the weighing chamber in such a way that it can be removed; a processor; a data input unit; and a data transmission path, over which data can be exchanged between the climate module and the processor. The object, according to a further formulation, is achieved with a climate module configured to electrically couple to a mass comparator in a detachable manner, wherein the climate module forms a self-contained modular unit and comprises an air pressure sensor, an air humidity sensor and an air temperature sensor, as well as a data transmission path, over which data can be sent to a processor external to the climate module.

The invention makes use of the idea of combining all of the components and functions, which are necessary for compensating for the climate changes in the weighing values, in the mass comparator. Therefore, no external computers, sensors, etc. are necessary. Instead, the user can be provided with a compact measurement laboratory, which can be designed in such a way that it is even portable. Since the climate module is interchangeable (i.e., can be detached from the balance without destroying it), it can be sent, if desired, to an external institute or service provider for calibration. In the meantime the mass comparator can still be used by installing a replacement climate module. As a result, it is possible to have on a rolling basis one or (in the case of several mass comparators) a plurality of climate modules being calibrated, while measuring with the other climate modules.

The climate module offers an additional advantage that older balances can be retrofitted. The only requirement for such a retrofitting is, in addition to the data transmission path, the software of the processor.

In terms of accuracy the mass comparator of the invention has the advantage that the climate data are measured behind the draft shield (and not just in the chamber, in which the balance is located). Therefore, precisely the air density that is relevant to the buoyancy is determined. In addition, since the buoyancy values are transmitted automatically to the processor, transmission errors can be virtually eliminated. According to the German patent DE 299 12 867 U1, such transmission errors are possible, for example, when transferring values from the so-called calibration certificate into the calibration software.

According to one embodiment, it is provided that the climate module is connected to the processor via an electrical plug-in connection. The plug-in connection can be integrated into a mechanical receptacle, which is used to attach the climate module to the precision balance. In this way the data transmission path to the processor is automatically established, when the climate module is installed inside the draft shield.

According to an alternative embodiment, it is provided that the climate module is coupled to the processor over a wireless transmission. In this case the climate module can be disposed at any location inside the draft shield, for example, on a partition wall, where it will interfere the least, without having to take into consideration whether a plug-in connection can be arranged at this location in such a way that it is useful. In addition, the absence of a plug-in connection has the advantageous effect that the interior of the weighing compartment can be designed to be smoother and, therefore, easier to clean.

Preferably the climate module includes an air pressure sensor, an air humidity sensor and an air temperature sensor. These sensors can be used to record the climate data that are essential for a precise measurement.

In addition, it can be provided that inside of the climate module there is a sensor for determining the degree of ionization in the weighing chamber; and this sensor is coupled to the data transmission path. As a result, an additional parameter can be determined and taken into account in the correction of the weighing result. The processor generates, as a function of a certain degree of ionization, an output signal, for example, to actively change the degree of ionization, by using an ionization device, which is activated after reaching certain degrees of ionization. Furthermore, a display can also indicate to the user that the degree of ionization inside the weighing chamber is too high and should be discharged.

It can also be provided that the climate module has a light sensor, which is coupled to the processor. Such an arrangement allows another parameter to be determined and taken into account in correcting the weighing result. The processor can output an output signal following a specified level of incident light. As a result, it is possible to determine the effect of the incident light on the weighing process, so that appropriate steps can be taken in the process itself. The output signal can also be an indicator.

According to one embodiment, it is provided that the processor is designed such that it uses the air pressure, the air humidity and the air temperature in the weighing chamber to determine, based on the density of the sample to be weighed, the air buoyancy of at least one test sample as well as to determine the buoyancy correction factor. This arrangement makes it possible to receive from the climate module the metrologically traceable values at the same time as the transfer of the mass value, with which the processor is able to correct the weighing result.

According to one embodiment, an electronic memory, in particular, an EEPROM, which can be read out by an external reader and in which the calibration values and the correction values for the climate module can be stored, is provided inside the climate module. In order to make adjustments, the calibration values can be stored in an electronic memory on the climate module, in particular, can be stored in an EEPROM. This is done at an external service provider. If the climate module is then reconnected to the mass comparator, these data are then immediately available to the processor of the balance. In addition, the memory can be used to store, among other things, at least some of the following sensor calibration data, for example: the number of the calibration certificate, the current calibration values, the calibration date, the name of the calibration laboratory, the name of the person in charge and the calibration history. In addition, so-called uncertainty values can also be stored for each climate variable in the memory of the climate module, so that, for example, in order to compute the air density, the computation of the uncertainty of the air density can also be performed by the mass comparator.

According to one embodiment, it is provided that the climate module can also be used as a stand-alone unit external to a balance and can be connected to a USB port of a PC via an I²C bus. This arrangement makes it easier to perform an external calibration. In addition, the climate module can be used in other applications to record climate variables without having to be connected to a balance. For this purpose the printed circuit board of the climate module can easily have a plug-in extension, in order to be connected to a USB adapter.

Furthermore, the object, according to yet another formulation of the invention, is achieved with a method for operating a mass comparator comprising a weighing chamber, which is separated from the surrounding area by a draft shield and in which an air pressure sensor, an air humidity sensor and an air temperature sensor are arranged, wherein the sensors are coupled to a processor and wherein the sample to be weighed is weighed in the form of a test sample and at least one reference weight. In this case it is provided that the air pressure, the air humidity and the air temperature in the weighing chamber are determined by the sensors. In addition, the density of the sample to be weighed, the mass of which sample is to be determined, is entered into the mass comparator. Furthermore, the air buoyancy of at least the test sample as well as the buoyancy correction factor are determined from the air pressure, the air humidity, the air temperature and the density of the sample to be weighed. Finally the corrected, conventional weighing value of the test sample is determined.

The inventive method determines the current air density during the weighing process from a number of parameters in the weighing chamber and not only, as proposed in DE 299 12 867 U1, with the air pressure. The actual current density and the density of the sample to be weighed are used to determine the air buoyancy of at least the test sample as well as to determine the buoyancy correction factor and, thus, the corrected conventional mass. Except for the density input, all other data items are entered automatically. That is, neither the temperature, the air humidity, nor the air pressure is entered manually into the processor; the data flow electronically via the sensors into the processor.

It is not absolutely necessary (but is not excluded) that two different reference weights or reference bodies be used to determine the density; instead, it is also possible to work with one reference weight.

It is also possible to compensate the measured values for changes inside the load cell due to climate changes.

The measurement of the corresponding data to determine the buoyancy in the draft shield has the advantage that precisely the air density that is relevant to the buoyancy is determined.

Due to the fact that the buoyancy values are transmitted automatically to the processor, it is possible to virtually eliminate transmission errors, which are possible, according to the German patent DE 299 12 867 U1, in the course of transferring the values from the so-called calibration certificate into the calibration software.

Not only the air buoyancy of the sample to be weighed, the weight of which is to be determined, but also the air buoyancy of the reference weight is determined from the air pressure, the air humidity and the air temperature as well as the density of the reference weight, in order to determine the mass of the reference weight, where the mass is corrected by its air buoyancy.

In addition, it can be provided that the degree of ionization in the weighing chamber is determined, and that the processor outputs an output signal, as a function of the degree of ionization that is determined. It can also be provided that a light sensor determines the level of incident light in the weighing chamber; and preferably that the processor outputs an output signal after a specified level of incident light. With respect to the advantages, reference is made to the above explanations.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will become apparent from the following description and from the following drawings, to which reference is made. The drawings show in:

FIG. 1 an exploded view of a mass comparator, according to the invention,

FIG. 2 a perspective view of an inventive climate module, which can be used in the mass comparator of the invention,

FIG. 3 a side view of the climate module from FIG. 2 without the outer housing,

FIG. 4 a plan view of the climate module from FIG. 2, also without the outer housing, and

FIG. 5 a flow chart showing the process of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a high resolution electronic mass comparator that in this exemplary embodiment permits mass comparisons to be performed for the accuracy classes E1-F2 in compliance with OIML R 111-1.

The mass comparator comprises a load cell 14 with a base 12, in which a weighing module 10, which is not shown in more detail, is housed. In addition, the load cell 14 comprises a weighing chamber 16, which is formed by a draft shield with adjustable side walls 18, a front wall 20 and a rear wall 22. The weighing chamber 16 is separated from the surrounding area by the draft shield. A weighing dish 24 is used to hold the sample to be weighed.

An electronic evaluation system 26, which is designed as a separate part in this embodiment, is electronically coupled to the load cell 14 via a cable 28. A display unit 30, which is coupled to the evaluation system 26, is used both as a display and as a data input unit. While the electronic evaluation system 26 and the display 30 are embodied as components physically separated from the weighing module 10 in the illustrated embodiment, other embodiments can incorporate one or both of these components 26 and 30 into the weighing module 10.

The electronic evaluation system 26 houses, among other things, a processor 32, which receives data from the load cell 14.

The weighing chamber 16 has a climate module 34, which is designed as a structurally separate unit and which can be mechanically coupled to the rear wall 22 through a disconnectable plug-in connection (hence, is attached in a manner allowing the climate module to be disconnected without destroying it), and, in particular, preferably without the aid of a tool.

For this purpose the rear wall 22 has two slots 36, which are spaced apart from each other and in which flexible locking hooks 38 (see also FIG. 2) engage with the outer housing 40 of the climate module.

FIGS. 2 to 4 show the climate module 34 in more detail.

The outer housing 40 has a number of apertures 42, through which the interior of the outer housing 40 changes over into the weighing chamber 16 and becomes a part of the weighing chamber 16, so that the climate inside the weighing chamber 16 corresponds to the climate inside the outer housing 40.

The climate module 34 is electronically coupled via an electrical plug-in connection to a corresponding plug receptacle 44 in the rear wall 22. The plug receptacle 44 is electrically connected to the processor 32. A plug 46 with contacts 48 is plugged into the plug receptacle 44 on the climate module 34. As a result, the plug 46 forms a module-sided part of the electrical plug-in connection.

As an alternative to an electrical plug-in connection, a wireless transmission, such as WLAN or Bluetooth, can be used.

The electrical plug-in connection (or the wireless transmission used as an alternative) forms a data transmission path, over which the data can be transferred from the climate module 34 to the processor 32 and, if desired, can be transferred back to the climate module.

The plug 46 is preferably a section of a circuit board 50, on which a plurality of sensors for detecting the climate in the weighing chamber 16 are disposed. Therefore, an air temperature sensor 52, an air humidity sensor 54, a light sensor 56, which is arranged directly in the vicinity of an aperture 42, and a sensor 58 for detecting the degree of ionization in the weighing chamber 16 are provided on the circuit board 50, and an electronic memory 60 is also provided on the circuit board. An air pressure sensor 62 is mechanically and electrically coupled to the circuit board 50 with a bracket 64.

A plurality of the sensors can also be combined into combined sensors.

A wall 66 closes the shell-like outer housing 40, so that the narrow tongue-like section of the circuit board 50 that is located to the right of the wall 66 in FIG. 4, can be inserted into the rear wall 22 and the plug receptacle 44.

Each sensor is coupled to the processor 32 via corresponding contacts 48. Similarly the memory 60 is coupled to the processor 32.

The mass comparator operates according to the following method, which is explained with reference to FIG. 5.

In the steps 100 and 102 the density of the sample to be weighed (test weight, also called the test sample B, and the reference weight A) is entered into the mass comparator, for example, using the display unit 30, which is also used simultaneously as a data input unit by way of, for example, the touch screen. As an alternative, the density of the sample to be weighed can have already been stored.

A sample to be weighed is placed on the weighing dish 24, and, in particular, according to the specified process steps, for example, first the reference weight A, then twice the test sample B and finally again the reference weight A. These process steps relate to comparison weighing, which in step 104 results in the display of the difference of the balance.

The air pressure, the air humidity and the air temperature can be determined in step 106 by the sensors 62, 54 and 52, respectively; and the corresponding data are then transmitted to the processor 32.

The air density is determined in the processor 32 (see step 108). The input densities of the reference weight A and the test sample B are used in the processor to determine the air buoyancy correction factor in step 110 and/or to determine the air buoyancy of the sample to be weighed, as a function of the air pressure, the air humidity, the air temperature as well as the density of the sample to be weighed; and in step 112 the conventional weighing result of the test sample B, i.e., the mass of the test sample B that is corrected by its air buoyancy, is determined and displayed as a protocol in the display unit 30, where in this case the conventional mass 114 of the reference weight also enters into the determination of the conventional mass of the test sample.

In addition, the calibration values and the correction values for the climate module 34, which had been input during the calibration of the climate module 34, are stored in the memory 60.

This calibration is performed outside of the mass comparator. To this end the climate module 34 is simply unplugged from the weighing chamber 16 without having to disconnect a wire connection. Then the climate module 34 is sent to an appropriate calibration institute that stores the number of the calibration certificate, i.e., the new calibration values, the calibration date, the name of the calibration laboratory, the name of the person in charge and the calibration history in the memory 60. These values are read out later by the application program, when the climate module 34 is once again in the mass comparator, and flow directly into the computation.

Even the values of the light sensor 56 and the sensor 58 for determining the degree of ionization in the weighing chamber 16 are determined.

For example, when the level of incident light increases, a corresponding signal will be shown on the display that, for example, the measurement is uncertain due to increased exposure to sunlight and, thus, due to a temperature change in the weighing chamber. As a result, the processor sends an output signal as a function of the exposure to incident light.

As soon as the degree of ionization is too high, an ionization device is activated; and this ionization device ionizes the air in the weighing chamber and makes sure that the sample to be weighed is discharged, or a warning about an excessive charge of the sample to be weighed is sent.

The memory 60 is preferably an EEPROM.

In addition, the connection between the climate module 34 and the rest of the mass comparator is implemented using an I²C bus.

The climate module 34 can be connected to a computer via a USB adapter, into which the climate module is inserted, in order to calibrate the sensors 52 to 58 and 62 without having to connect the climate module 34 to the mass comparator.

As can be seen, the climate module is designed so that it can also be used as a stand-alone unit outside a balance and can be connected to a USB port of a PC using an I²C bus.

LIST OF REFERENCE NUMERALS AND CHARACTERS

-   10 weighing module -   12 base -   14 load cell -   16 weighing chamber -   18 side wall -   20 front wall -   22 rear wall -   24 weighing dish -   26 evaluation system -   28 cable -   30 display unit -   32 processor -   34 climate module -   36 slots -   38 locking hooks -   40 outer housing -   42 apertures -   44 plug receptacle -   46 plug -   48 contacts -   50 printed circuit board -   52 air temperature sensor -   54 air humidity sensor -   56 light sensor -   58 sensor -   60 memory -   62 air pressure sensor -   64 bracket -   66 wall -   100 step -   102 step -   104 step -   106 step -   108 step -   110 step -   112 step -   114 conventional mass of the reference weight -   A reference weight -   B test sample 

What is claimed is:
 1. Method for operating a mass comparator that comprises a weighing chamber, which is separated from a surrounding area by a draft shield and in which an air pressure sensor, an air humidity sensor, and an air temperature sensor are disposed, wherein the sensors are coupled to a processor, and that is configured to weigh a test sample and at least one reference weight, said method comprising: determining the air pressure, the air humidity and the air temperature in the weighing chamber with the sensors; entering a density of the test sample into the mass comparator; determining an air buoyancy of at least the test sample and/or a buoyancy correction factor in accordance with the air pressure, the air humidity, the air temperature and the density of the test sample; and determining a corrected, conventional weighing value of the test sample (B).
 2. The method as claimed in claim 1, further comprising determining a degree of ionization in the weighing chamber; and outputting an output signal from the processor in accordance with the degree of ionization.
 3. The method as claimed in claim 1, further comprising determining incident light with a light sensor in the weighing chamber.
 4. The method as claimed in claim 3, further comprising outputting an output signal from the processor in response to a predetermined incident light level.
 5. The method as claimed in claim 1, wherein at least some of the sensors are housed in a climate module that is configured to decouple from a remainder of the mass comparator, further comprising: storing calibration values and correction values in a memory of the climate module; and calibrating the mass comparator after detaching the climate module from the remainder of the mass comparator. 